In recent years, studies have been conducted on the technology for manufacturing a device by bonding two types of substrates at room temperature. For example, Japanese Unexamined Patent Application Publication No. 10-092702 discloses a silicon wafer bonding method that does not require loading and pressing or a heat treatment but achieves a large bonding strength. This room-temperature silicon wafer bonding method includes bonding a silicon wafer to a silicon wafer, in which bonding surfaces of the two silicon wafers are sputter-etched by being irradiated with an inert gas ion beam or an inert gas fast atom beam in vacuum at room temperature prior to bonding.